

McqMate
These multiple-choice questions (MCQs) are designed to enhance your knowledge and understanding in the following areas: Electrical Engineering .
1. |
The main function of a fuse is to |
A. | protect the line |
B. | open the circuit |
C. | protect the appliance |
D. | prevent excessive currents |
Answer» D. prevent excessive currents |
2. |
On which of the following routine tests are conducted? |
A. | Oil circuit breakers |
B. | Air blast circuit breakers |
C. | Minimum oil circuit breakers |
D. | All of the above |
Answer» D. All of the above |
3. |
SF6 gas |
A. | is yellow in colour |
B. | is lighter than air |
C. | is nontoxic |
D. | has pungent small |
Answer» C. is nontoxic |
4. |
The arcing contacts in a circuit breaker are made of |
A. | copper tungsten alloy |
B. | porcelain |
C. | electrolytic copper |
D. | aluminium alloy |
Answer» A. copper tungsten alloy |
5. |
Which of the following medium is employed for extinction of arc in air circuit breaker ? |
A. | Water |
B. | Oil |
C. | Air |
D. | SF6 |
Answer» C. Air |
6. |
With which of the following, a circuit breaker must be equipped for remote operation ? |
A. | Inverse time trip |
B. | Time-delay trip |
C. | Shunt trip |
D. | None of the above |
Answer» C. Shunt trip |
7. |
Fault diverters are basically |
A. | fuses |
B. | relays |
C. | fast switches |
D. | circuit breakers |
Answer» C. fast switches |
8. |
A thermal protection switch can protect against |
A. | short-circuit |
B. | temperature |
C. | overload |
D. | over voltage |
Answer» C. overload |
9. |
Arc in a circuit behaves as |
A. | a capackive reactance |
B. | an inductive reactance |
C. | a resistance increasing with voltage rise across the arc |
D. | a resistance decreasing with voltage rise across the arc |
Answer» D. a resistance decreasing with voltage rise across the arc |
10. |
Thermal circuit breaker has |
A. | delayed trip action |
B. | instantaneous trip action |
C. | both of the above |
D. | none of the above |
Answer» A. delayed trip action |
11. |
Relays can be designed to respond to changes in |
A. | resistance, reactance or impedance |
B. | voltage and current |
C. | light intensity |
D. | all above |
Answer» D. all above |
12. |
Overload relays are of…… type. |
A. | induction |
B. | solid state |
C. | thermal |
D. | all above |
Answer» D. all above |
13. |
Thermal overload relays are used to protect the motor against over current due to |
A. | short-circuits |
B. | heavy loads |
C. | grounds |
D. | all of the above |
Answer» B. heavy loads |
14. |
Magnetic circuit breaker has ______ trip action. |
A. | delayed |
B. | instantaneous |
C. | both of the above |
D. | none of the above |
Answer» B. instantaneous |
15. |
D.C. shunt relays are made of |
A. | few turns of thin wire |
B. | few turns of thick wire |
C. | many turns of thin wire |
D. | many turns of thick wire |
Answer» C. many turns of thin wire |
16. |
The relay operating speed depends upon |
A. | the spring tension |
B. | the rate of flux built up |
C. | armature core air gap |
D. | all of the above |
Answer» D. all of the above |
17. |
In order that current should flow without causing excessive heating or voltage drop, the relay contacts should |
A. | have low contact resistance |
B. | be clean and smooth |
C. | be of sufficient size and proper shape |
D. | have all above properties |
Answer» D. have all above properties |
18. |
Circuit breakers usually operate under |
A. | transient state of short-circuit current |
B. | sub-transient state of short-circuit current |
C. | steady state of short-circuit current |
D. | after D.C. component has ceased |
Answer» A. transient state of short-circuit current |
19. |
Circuit breakers are essentially |
A. | current carrying contacts called electrodes |
B. | arc extinguishers |
C. | circuits to break the system |
D. | tr |
Answer» A. current carrying contacts called electrodes |
20. |
The current zero interruption, in oil and air blast circuit breakers, is achieved by |
A. | lengthening of the gap |
B. | cooling and blast effect |
C. | both (a) and (b) |
D. | deionizing the oil with forced air |
Answer» C. both (a) and (b) |
21. |
Air blast circuit breaker is used for |
A. | over currents |
B. | short duty |
C. | intermittant duty |
D. | repeated duty |
Answer» D. repeated duty |
22. |
An efficient and a well designed protective relaying should have |
A. | good selectivity and reliability |
B. | economy and simplicity |
C. | high speed and selectivity |
D. | all of the above |
Answer» D. all of the above |
23. |
Burden of a protective relay is the power |
A. | required to operate the circuit breaker |
B. | absorbed by the circuit of relay |
C. | developed by the relay circuit |
D. | none of the above |
Answer» B. absorbed by the circuit of relay |
24. |
Directional relays are based on flow of |
A. | power |
B. | current |
C. | voltage wave |
D. | all of the above |
Answer» A. power |
25. |
A differential relay measures the vector difference between |
A. | two currents |
B. | two voltages |
C. | two or more similar electrical quantities |
D. | none of the above |
Answer» C. two or more similar electrical quantities |
26. |
A transmission line is protected by |
A. | inrush protection |
B. | distance protection |
C. | time graded and current graded over current protection |
D. | both (b) and (c) |
Answer» D. both (b) and (c) |
27. |
Large internal faults are protected by |
A. | merz price percentage differential protection |
B. | mho and ohm relays |
C. | horn gaps and temperature relays |
D. | earth fault and positive sequence relays |
Answer» A. merz price percentage differential protection |
28. |
When a transmission line is energized, the wave that propagates on it is |
A. | current wave only |
B. | voltage wave only |
C. | both (a) and (b) |
D. | power factor wave only |
Answer» C. both (a) and (b) |
29. |
Protective relays are devices that detect abnormal conditions in electrical circuits by measuring |
A. | current during abnormal condition |
B. | voltage during abnormal condition |
C. | constantly the electrical quantities which differ during normal and abnormal conditions |
D. | none of the above |
Answer» C. constantly the electrical quantities which differ during normal and abnormal conditions |
30. |
The voltage appearing across the contacts after opening of the circuit breaker is called______voltage. |
A. | recovery |
B. | surge |
C. | operating |
D. | arc |
Answer» A. recovery |
31. |
Ionization in circuit breaker is facilitated by |
A. | high temperature |
B. | increase of mean free path |
C. | increasing field strength |
D. | all of the above |
Answer» D. all of the above |
32. |
In a circuit breaker the basic problem is to |
A. | maintain the arc |
B. | extinguish the arc |
C. | transmit large power |
D. | emit the ionizing electrons |
Answer» C. transmit large power |
33. |
Overheating of relay contacts or contact born out is due to |
A. | slow making and breaking of load circuit contacts |
B. | foreign matter on the contact surface |
C. | too low contact pressure |
D. | all of the above |
Answer» D. all of the above |
34. |
Interruption of large currents by relay requires |
A. | arc suppressing blow out coils |
B. | wide separation of the opened contacts |
C. | high speed opening of contacts |
D. | all of the above |
Answer» D. all of the above |
35. |
Shunt capacitance is neglected while considering |
A. | short transmission line |
B. | medium transmission line |
C. | long transmission line |
D. | medium and long tr |
Answer» A. short transmission line |
36. |
The arc voltage produced in A.C. circuit breaker is always |
A. | in phase with the arc current |
B. | lagging the arc current by 90″ |
C. | leading the arc current by 90° |
D. | none of the above |
Answer» A. in phase with the arc current |
37. |
The time of closing the cycle, in modern circuit breakers is |
A. | 0.003 sec |
B. | 0.001 sec |
C. | 0.01 sec |
D. | 0.10 sec |
Answer» A. 0.003 sec |
38. |
Insulation resistance of high voltage circuit breakers is more than |
A. | 1 mega ohms |
B. | 10 mega ohms |
C. | 100 mega ohms |
D. | 500 mega ohms |
Answer» C. 100 mega ohms |
39. |
H.R.C. fuses provide best protection against |
A. | overload |
B. | reverse current |
C. | open-circuits |
D. | short-circuits |
Answer» D. short-circuits |
40. |
The ground wire should not be smaller than No ______ copper. |
A. | 2 |
B. | 4 |
C. | 6 |
D. | 10 |
Answer» D. 10 |
41. |
The delay fuses are used for the protection of ________ . |
A. | motors |
B. | power outlet circuits |
C. | fluorescent lamps |
D. | light circuits |
Answer» A. motors |
42. |
Which of the following is the least expensive protection for overcurrent is low voltage system ? |
A. | Rewireable fuse |
B. | Isolator |
C. | Oil circuit breaker |
D. | Air break circuit breaker |
Answer» A. Rewireable fuse |
43. |
Resistance grounding is used for voltage between |
A. | 33kVto66kV |
B. | HkVto33kV |
C. | 3.3kVandllkV |
D. | none of the above |
Answer» C. 3.3kVandllkV |
44. |
The contacts of high voltage switches used in power system are submerged in oil. The main purpose of the oil is to |
A. | lubricate the contacts |
B. | insulate the contacts from switch body |
C. | extinguish the arc |
D. | all of the above |
Answer» C. extinguish the arc |
45. |
In Railway applications ______ circuit breaker is used. |
A. | SFe |
B. | bulk oil |
C. | minimum oil |
D. | air break |
Answer» D. air break |
46. |
To protect most of the electrical equipment handling low power, the types of relays used are |
A. | thermocouple |
B. | electronic and bimetallic |
C. | both (a) and (b) |
D. | none of the above |
Answer» C. both (a) and (b) |
47. |
Wave trap is used to trap waves of |
A. | power frequencies |
B. | higher frequencies entering generator or transformer units |
C. | either of the above |
D. | none of the above |
Answer» B. higher frequencies entering generator or transformer units |
48. |
Ungrounded neutral transmission system is not recommended because of system |
A. | insulation being overstressed due to over voltages |
B. | insulation overstress may lead to failure and subsequent phase to phase faults |
C. | being inadequately protected against ground fault |
D. | all of the above |
Answer» D. all of the above |
49. |
The reflection co-efficient at the open circuited end of a transmission line. |
A. | zero |
B. | infinity |
C. | unity |
D. | none of the above |
Answer» C. unity |
50. |
For the protection of power station buildings against direct strokes the requirements are |
A. | interception |
B. | interception and conduction |
C. | interception, conduction and dissipation |
D. | interception, conduction, dissipation and reflection |
Answer» C. interception, conduction and dissipation |
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